1. Field of the Invention
The present invention relates to a data acquisition device used with a machine tool.
2. Description of the Related Art
In an at least a partially automated machining system using a machine tool controlled by a numerical control device, it is important to reduce time required to complete a series of steps, i.e., reduce cycle time, in order to improve productivity. Cycle time mainly consists of working time during which at least one drive axis of the machine tool is in operation, and stoppage time during which no drive axis is in operation. There is a correlation between the working time and machining accuracy: Machining accuracy generally tends to decrease, as the working time is shortened. Accordingly, it is necessary to reduce the stoppage time in order to reduce the cycle time.
Existing data acquisition devices are generally designed to acquire data representative of operational information of drive axes of the machine tool, and information on a machining program from the numerical control device. An operator can only ascertain the stoppage time of the drive axes, and information on the active portion of the program when the drive axes are in a stopped state. For this reason, it is necessary for the operator to attempt to reduce the stoppage time by guessing the cause of stoppage of the drive axes in order to adjust the machining program or parameters.
JP-A-2011-39708 discloses a control system for a machine tool designed to obtain a reference value of cycle time and its variance from actual sampling signals, and automatically detect irregularity by comparing the cycle time to complete the machining process with the reference value. JP-A-2011-39708 discloses acquiring a block number of the machining program simultaneously with the sampled information, so as to allow an operator to easily check the relationship between the sampled result and the machining program.
JP-A-2010-92405 discloses a numerically controlled machine tool designed to display a time chart of machining load during a machining process and a corresponding machining program on the same screen of a display device, so as to allow the machining program to be efficiently modified in accordance with magnitude of the machining load.
However, according to the existing data acquisition device, the cause of stoppage of drive axis has not been identified, and thus it is necessary to reduce the stoppage time of the drive axis through try-and-error, which requires intensive labor and/or enormous time. Accordingly, there is a need for a data acquisition device for providing an operator with useful information in order to efficiently reduce the stoppage time of the drive axis.